Apparatus for bending pipe



Decr23, 1947. w. R. LINDEN ETAL 2,433,055

APPARATUS FOR BENDING PIPE Filed Dec. 20, 1944 I" l IIIIIIIIIIIIIIIIIIIIII.

INVENTORS WA]. TER R. l. INDEN IYERBERT H. MOSS ATTORNEY um. Such fuel gases Patented Dec. 23, 1947 UNITED STATESPATENT OFFICE APPARATUS Z Z B ZNDING PIPE Walter R. Linden,

Moss, Elizabeth, N.

to pipe bending and to progressive upset bending Palisades Park, and Herbert H.

1., minors to The Linde Air Products Company, a corporation of Ohio Application December 20, 1944,. Serial No. 589,078

3 Claims. 153-32) A method of bending such pipe has been deveioped. known as Wrinkle bending, which in volves wrinkling the pipe outwardly so that the pipe, with its. length shortened slightly on one side by wrinkling,

deviates from a true line by the angle resulting from the wrinkle. In practice, flame is used to heat one or more axially spaced bands at right angles to the longitudinal axis of the pipe and extending more than halfway around the circumference of the pipe. The pipe is then bent either by hand or mechanically by slightly buckling such bands. As a rule, wrinkling is used to produce only a slight change in direction of the pipe. When the direction is more pronounced, a. series of wrinkles provide a more abrupt bend. Wrinkle bending, has found its greatest use in overland gas and oil piping for curvature of relatively low degree.

Other known methods of bending pipe involve simply bending the pipe while cold or hot. However, the outer wall of "flre and cold" bends is definitely and objectionably thinned by the bending operation.

It has also been proposed to bend pipe by progressively flame heating, upsetting and chilling the metal as the bending operation proceeds, but such proposals, due probably to the relatively low temperature obtainable with a mixture of air and fuel gas, have not generally been adopted. In some cases the bend must be restored to a round section after the bending operation, especially in the case of large diameter pipe, or expensive and heavy apparatus, not at all suitable for field use, must be used. Also, such proposals involve the combustion of fuel gas and air, or propane and air, as the heating mediare not always'readily available to cross-country pipe laying gangs. Nor is it feasible in the field to fill a pipe to be bent with a core to maintain a round section.

Factory made bends and fittings are very expensive. As a result, there exists a very great demand for some satisfactory method of progressively bending 'pipe that can be carried out in the field by ordinary workmen, with light, simple equipment and a readily available source of heat.

The main object of this invention is to overcome disadvantages and difficulties of the prior art and provide a pipe bend that is stronger and more economical. Other objects are to provide an improved process and novel apparatus for bending metal pipe.

flames produced by against the pipe,

Such objects are accomplished, according to the invention, by subjecting the pipe to a suitable bending moment in the region to be bent, and then progressively heating, upsetting and chilling the metal in an extremely narrow transverse wall zone in such region, which zone moves axially from one end to the other of the bend as the bending operation proceeds. Such extremely narrow transverse wall zone is obtained, for-exampla by a flame composed of commercially pure oxygen and fuel gas (which has atomperature of the order of 1500 higher than an air and fuel gas flame) directed radially against the pipe wall with the inner cone of the flame only slightly spaced from the peripheral surface of the pipe. By virtue of its high heat intensity, such oxy-fuel gas flame causes rapid heating of the metal to a temperature slightly below the mushy stage in a very narrow wall zone, and upsetting Y of the heated metal takes place before the high temperatureheat is transmitted to the adjacent metal. Such upsetting rapidly progresses to a value of to 133% or more of the initial wall thickness, and the upset metal is chilled directly after being upset. The oxy-fuel gas heating flame may be produced by a suitable blowpipe head having internal ports or tips which direct a suitable mixture of the oxygen and fuel gas the pipe and'head being moved relatively to each other in the direction of the bend, without substantially changing their relative transverse positions.

According to the invention, pipe bending is accomplished by the continuous upsetting of axially small increments of metal, providing the facility of variable bend radii, nominal wall thickness on the outside of the bend, and a reinforced inside wall giving the bend great strength. The invention makes it possible, with simple and readily available materials, to obtain a truly circular pipe bend by progressive and continuous incremental upsetting without thinning the outer wall or damaging the metal aflected by the upsetting process. Damage to high strength pipe, if any, can be corrected by subsequent heat treatment by the device of the invention, if desired.

A critical and novel feature of the invention is the employment of at leastfone row of hightemperature oxy-fuel gas flames which embraces the circumference of the pipe only in the compression zone thereof.

The invention involves a process of bending commercial pipe and tubing by upsetting that portion of the metal lying in the compression area of the fiexural diagram for simple bending 3 (I by the application of heat of sufllcien't intensity to quickly change the temperature of a very narrow band of the metal in such portion to a. value slightly below the mushy stage, the heat being derived from oxy-acetylene flames having a temperature of' the order of 5,600 F. for a 1.5/1 ratio of oxygen to acetylene, progressively applied from the point of bend origin to the opposite or second point of tangency. The heating zone is so disposed as to shift the normal neutral axis of the tubular section to a point sufllcientiy close to the metal in the region of the outer radius or tension portion of the tubular section so as to minimize the intensity of the tensile stress therein during the bending operation. The result is rapid reorientation of the metal only in the flexural plane normal to the longitudinal axis of the bend.

In the drawing: I

Fig. 1 is a fragmentary view in side elevation of apparatus illustrating the invention;

Fig. 2 is a fragmentary view in front elevation taken on line 2-2 of F18. 1;

Fig. 3 is a fragmentary view mainly in crosssection of the head;

Fig. 4 is a view mainly in rear elevation taken on line 4-4 of Fig. 3; 1

Fig. 5 is a horizontal sectional view taken on line 5-5 of Fig. 4;

Fig. 6 is a longitudinal sectional view of a pipe bent according to the invention; and

Fig '7 is an enlarged transverse sectional view of the pipe taken on line 1-4 of Fig. 6.

The reorientation of the metal in the plane 1-1 of. bending produces two eccentric circles having radii R and R1 (the centers of which have an eccentricity E) when viewed from the standpoint of the inner and outer walls of the section, as shown in Fig. 7, and of such relation that the thickness of wall A is substantially that of the pipe wall before bending at B," the increase being proportional to the decrease in length of the metal required to be upset to form a specific pipe bend C. Accurate control of upsetting is accomplished by chilling the metal quite close. to the zone of upsetting and progressing therewith as the bend is being made, which in eifect operates to reestablish the normal temperature structural property of the tubular section close to the plastic zone directly following upset. This operates to constrain the heated metal to the initial circular shape. The present upset method of bending pipe produces a true and uniform bend C possessing a reinforced inner wall B and, in turn, making for a stronger bend in service because of the increased strength in that portion A of the bend subject to tension.

In the illustrated apparatus, which is shown only by way of example. a base 18 is provided with uprights l2 near the top of which is mounted a pulley H over which a chain i6 passes. The chain is provided with a hook l8 which is inserted in one end of the pipe P to be bent, and a pulling force is applied to the other end of the chain iii. For this purpose the chain may be 'wound on a Windlass not shown, which may be turned by hand or by a motor. A pair of vises 28 are also mounted on the base It! for anchorin the main section of the pipe P, asthe upward bending force is applied to the free end thereof through the chain It.

An oxy-acetylene blowpipe 22 is mounted in a fitting 28 which is pivoted to the uprights i2 in suitable bearings 28. Mounted on the blowpipe 22 is a novel head 28 consisting of an oxy-acetylene heating flame section 30, a chilling section 22 and a pipe bearing section 84. The oxy-acetylene heating flame section is provided with an oxy-acetylene distributing passage 28 having a row of ports 88 for discharging a suitable combustible mixture of oxygen and acetylene inwardly of the head to form jets which, when ignited, produce characteristic oxy-acetylene heating flames or very high temperature and intensity. The chilling section 82 of the head 28 is provided with a chilling fluid distribution passage l0, and a row of chilling fluid outlet passages ll which are arranged in rearwardly inclined relation to the oxy-acetylene gas ports 38, and are adapted to discharge streams of cooling fluid such as water against the pipe P. The chilling water streams are placed as close as possible tothe oxy-acetylene flames. The pipe hearing section 24 of the head 28 is provided with diametrically opposed pipe bearing surfaces 42 which are adapted to slidably engage and prevent the pipe wall from collapsing or expanding laterally during the bending operation. For pipes of small diameter the bearings 42 may be omitted, but they may be desirable in some cases for pipes of large diameter. Also, roller or ball bearings may be used, if desired.

Commercially pure oxygen and fuel gas, in this case acetylene, are supplied to the blowpipe 22 through suitable flexible conduits O and A; and water is supplied to the head 28 through a suitable flexible hose W.

Inorder to correlate movement of the head 28 with the bending of the pipe P, the fitting 24 in which the blowpipe 22 is mounted, is provided with an arm 44, the outer end portion of which passes through an opening in a bracket 46 which is secured to the pipe P in substantially parallel relation to the longitudinal axis of the blowpipe 22, the longitudinal axis of the arm 44 being substantially parallel to that of the pipe P before being bent.

In operation, with the parts in the full line position shown in Fig. 1, oxygen and acetylene are supplied to the blowpipe 22 in which they are mixed and the resulting oxy-acetylene jets from the ports 88 are ignited. The oxy-acetylene flames are applied to the pipe P in an extremely narrow band which extends about of the way around the circumference of the pipe. The chain I6 is then tensioned to apply a suitable bending force to the free end of the pipe P, and water is supplied to the head H through hose W. The oxy-acetylene flames quickly heat an axially narrow zone ofmetalin the wall of the pipe P until such metal becomes sufficiently soft or plastic or reaches a forging temperature such that the metal is upset by the bending force in the compression area of the flexural diagram.

The head 28 is thereupon automatically advanced in the direction of the bend, as the bend progresses, by the bending movement of the pipe itself, acting through clamp 46, arm 44 and blowpipe 22. As the incremental zone of upset metal advances, the upset metal is chilled immediately after being upset, by streams of water from the ports ll in the head 28. The bearings 42 engage opposite sides of the pipe P as the head 28 advances during the formation of the bend, and prevent undue collapse or lateral expansion of the'pipe P. The bearings 42 also act to guide the head with respect to the pipe.

As a result. a bend C is produced as shown in Figs. 6 and 7. The wall thickness of the bend C is uniform in any longitudina1 plane through the pipe wall throughout the length of the bend.

well-lmown physical andverynarrowheatbandthatextendsatieast halt-way but not all the way arolmd the pipe. egood resultsmaybeobtainedwithaaingle rowofoxy-mel better-resultsmaybeobtainedbyoxy-iuelgas fiamesthesizeorheaflngvalueoiwhichincreases towamtheneutralaxisofthebendtheaverage widthoitheplasticheatbandorzonebeingof theorderotthewallthicknessofthepipe.

1y have on hand oxygen and acetylene or other tool gas supplies as well as simple apparatus gasflamesotuniformsiaestill,

which may be adapted for carrying out the inven- The wall thickness is uniform tromjone end of the bend to the other, with an increase in strength over thatoi' the same pipe prior to bending. The hend needs no reforming after the bending operanon. Theradiusorcm'v tureofthebendmay' be greater than, equal to or less than the diameter of the pipe. The invention is not generally a plicable to ordinary cast iron pipe, because o1 the and metallurgical characteristics of cast iron. It also is not generally applicable to wrought iron pipe, because the act of upsetting might afiectthe layers or striations oi iron and slag-like material therein which give wrought iron etc. well-known properties.

The proposals of the prior art will not work except in a shop having machinery for re-round. ing flattened pipe. The reason for flattening is mind in their use of a' low temperature heat source involving air (as distinguished from commercially pure oxygen) and fuel gas. Such a heat source covers a relatively wide area axially of the pipe. I! the heated area is wide with re: spect to the wall thickness, when force is applied awrinklewilloccur. Iithepipeisheatedina wide hand all the way round, then fla or ovaling on the far side together with thinning of upsetting force, it the to the localized. high correct.

relation of machine speed temperature heat band is temperature of about ure xygen. ical range oi steel is about 1350 oxy-iuel gas flame results in a marked improvement over the prior art ploying air-fuel gas While an oxy-tuel gas flame, i. e., a flame produced by 8 suitable Since the crit- F.1600 E, the

heating mediums, such as the electric arc surrounded by air or helium, and high-frequency induction heating, which concentrate the heat appliedto the pipe in a very narrow band the a 7 width of which is of the order ot the thickness of the wall or the pipe.

What is claimed is:

1. Pipe bending apparatus including a blowpipe having a head provided with fuel gas outlets, means supporting said blowpipe for tilting movement, and means acting to tilt said blowpipe comprising a member connected to said supporting means, and a member connected to the pipe and slidably engaging the first member so as to form a parallelogram with the blowpipe and the pipe.

2. Pipe bending apparatus including a pipe heating head, means supporting said head for tilting movement, and means for tilting said head comprising a member connected to said supporting means, and a member connected to the pipe and slidably engaging the first member.

3. Pipe bending apparatus including a pipe heating head, means for supporting said head for 8 tilting movement, and means for tilting said head comprising members including an arm com to said head and a bracket connected to the pipe, the eflective length of which arm changes as the head is tilted with the bending of the pipe.

WALTER R LINDEN.

ERT H. MOSS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

